Reverse saturable absorbtion sensitizers for optical data storage media and methods for use

ABSTRACT

The invention relates generally to optical data storage media, and more specifically, to holographic storage media. In one embodiment, an optical storage medium composition includes a polymer matrix. Disposed within the polymer matrix is a reactant capable of undergoing a modification that alters the refractive index of the composition upon receiving an energy transfer from an excited sensitizer. A non-linear sensitizer is also disposed within the polymer matrix, and the sensitizer includes a metal-substituted subphthalocyanine (M-sub-PC) reverse saturable absorber configured to become excited upon exposure to light beyond an intensity threshold at approximately 405 nm and configured to transfer energy to the reactant.

BACKGROUND

The invention relates generally to optical data storage media, and morespecifically, to holographic storage media.

Optical storage media generally provide an effective platform forarchiving data, offering numerous advantages over other forms of datastorage in terms of cost of the medium, life expectancy of the storeddata, the amount of time required to write data, and the amount of timerequired to access the data. Holographic storage is a specific type ofoptical storage in which data is written to and read from the opticalmedium as holograms. These holograms are images formed by theinteraction of multiple beams of light in a photosensitive layer withinthe volume of a holographic medium. That is, for example, using acombination of a reference light beam and a signal light beam, athree-dimensional interference pattern may be formed in the holographicmedium as certain species present are chemically modified by the beams,modulating the refractive index of specific portions of the holographicmedium.

In such a holographic medium, a reverse saturable absorber (RSA) may beused as an energy-transfer threshold dye. In general, an energy-transferthreshold dye may be generally responsible for absorbing recording light(e.g., from the reference beam and signal beam) and causing a chemicalreaction to occur. That is, when the recording light is beyond aparticular intensity threshold, the RSA dye may be absorb multiplephotons of recording light and then transfer the energy of the excitedstate to a reactant species (e.g., an index change material). Inresponse, the reactant species may undergo a chemical reaction (e.g.,dimerization reactions, isomerization reactions, or inter- orintra-molecular condensation reactions), which may cause a localizedchange in the refractive index of the holographic medium, essentiallycapturing the intensity and phase of the recording light. Subsequently,upon interrogating the holograms using a lower intensity of light, thiscaptured information may be recovered in a nondestructive fashion suchthat the associated encoded data may be deciphered. However, the RSA dyeshould have sufficient sensitivity to enable efficient recording of datato the holographic medium.

BRIEF DESCRIPTION

In one embodiment, an optical storage medium composition includes apolymer matrix. Disposed within the polymer matrix is a reactant capableof undergoing a modification that alters the refractive index of thecomposition upon receiving an energy transfer from an excitedsensitizer. A non-linear sensitizer is also disposed within the polymermatrix, and the sensitizer includes a metal-substitutedsubphthalocyanine (M-sub-PC) reverse saturable absorber configured tobecome excited upon exposure to light having an intensity above anintensity threshold and configured to transfer energy to the reactant.

In another embodiment, a sensitizer having the general formula:

wherein:each X¹ independently comprises: a proton, a halide, an hydrocarbylgroup having between 1 and 10 carbons, or an alkoxy group having between1 and 10 carbons; and R¹ comprises any functional group or collection offunctional groups configured to bind a metal.

In another embodiment, a method for storing data on an optical mediumincludes irradiating a portion of the optical medium with recordinglight having an intensity above an intensity threshold, wherein theoptical medium comprises a metal-substituted subphthalocyanine(M-sub-PC) reverse saturable absorber (RSA) and a reactant disposedwithin a polymer matrix. The method also includes exciting the M-sub-PCRSA to an excited triplet state with the recording light such that theexcited M-sub-PC RSA sensitizes a modification of the reactant. Themethod also includes modifying the reactant such that the refractiveindex of the portion of the optical medium is altered, forming ahologram on optical medium, wherein the hologram stores informationabout the intensity and phase of the recording light.

DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is an energy level diagram illustrating excitation of thesensitizer and energy transfer to the reactant, in accordance withaspects of the present disclosure;

FIG. 2 is a graph illustrating the non-linear absorption of a thresholdsensitizer, in accordance with aspects of the present disclosure;

FIG. 3 is a cross-sectional view of an optical storage medium beingirradiated with recording light, in accordance with aspects of thepresent disclosure;

FIG. 4 illustrates examples of crown-ether-based M-sub-PC RSA dyes, inaccordance with aspects of the present disclosure;

FIG. 5 illustrates examples of diketone-based M-sub-PC RSA dyes, inaccordance with aspects of the present disclosure;

FIG. 6 illustrates examples of pyridine-based M-sub-PC RSA dyes, inaccordance with aspects of the present disclosure;

FIG. 7 is a schematic of a synthetic route for producingmetal-substituted 15-crown-5 ether-based RSA dyes, in accordance withaspects of the present disclosure;

FIG. 8 is a schematic of a synthetic route for producingmetal-substituted 18-crown-6 ether-based RSA dyes, in accordance withaspects of the present disclosure;

FIG. 9 is a graph illustrating the change in the refractive index ofthree different optical media being exposed to recording light ofvarying intensity, in accordance with aspects of the present disclosure;

FIG. 10 is a graph illustrating the quantum efficiency of threedifferent optical media being exposed to recording light of varyingintensity, in accordance with aspects of the present disclosure;

FIG. 11 is a schematic illustrating an embodiment of a quantumefficiency measurement setup for performing the quantum efficiencymeasurement; and

FIG. 12 is an embodiment of a graph illustrating an absorbance versusfluence plot.

DETAILED DESCRIPTION

It should be generally noted that, as used herein, “fluence” is ameasure of the amount of optical beam energy that has traversed a unitarea if the beam cross-section (e.g., in units of Joules/cm²), while“intensity”, also known as optical radiative flux density, is a measureof the energy that has traversed a unit area of the beam cross-sectionper unit time (e.g., in units of Watts/cm²). Furthermore, the term“quantum efficiency”, as used herein, is the probability an absorbedphoton will result in a chemical transformation that modulates therefractive index of an optical medium. Additionally, the “sensitivity”of a particular holographic medium generally refers to the quantumefficiency of a holographic medium (e.g., when recording light ofrelatively low intensity is used).

The disclosed embodiments describe optical media suitable forholographic data storage as well as methods for using such a platformfor data storage. Generally speaking, a holographic medium may include anon-linear sensitizer species and a reactant species disposed togetherin a polymer matrix. The non-linear sensitizer species may be a reversesaturable absorber (RSA) dye and, in particular, may be ametal-substituted subphthalocyanine (M-sub-PC) RSA dye. As described indetail below, these M-sub-PC dyes afford both the aforementionedenergy-transfer threshold behavior and relatively high quantumefficiencies when using relatively low-intensity recording light. Anoptical media utilizing these M-sub-PC RSA dyes afford greatersensitivity and efficiency during the recording process than othermaterials previously described.

Generally speaking, an RSA dye exhibits a non-linear response to therecording light (i.e., actinic radiation). FIG. 1 depicts an energydiagram 10 that illustrates the interactions of various energy levelspresent within an optical medium. More specifically, FIG. 1 illustratessome possible interactions between certain energy levels of a sensitizer12 (e.g., the M-sub-PC RSA dye), the reactant species 14, and theresulting product 16. In general, the sensitizer 12 in its ground state,S₀ 18, does not substantially absorb photons of the recording light.However, if the intensity of the recording light is beyond a particularthreshold, then the sensitizer 12 may become excited (e.g., via a firstphoton absorption 20) to reach an excited singlet state (e.g., S₁ 22).At some point after initial absorption 20, the sensitizer 12 may undergointersystem crossing (ISC) 24 to arrive at an excited triplet state(e.g., T₁ 26). This triplet state 26 may generally have a higherabsorption cross-section than the singlet ground state S₀ 18 and,accordingly, be a substantially stronger absorber of the recording light(i.e., a non-linear response to the actinic radiation). As such, thesensitizer 12 may absorb 28 another photon of the recording light toreach an excited triplet state RSA³* (e.g., T₂ 30). Accordingly, afterabsorbing two photons of the recording light, the sensitizer 12 may thentransfer 32 the energy of the excited triplet state (e.g., T₂ 30) to atriplet energy level (e.g., T₁ 34) of the reactant species 14 present inthe holographic medium. The reactant 14, having received this energytransfer, may subsequently chemically react (e.g., dimerize with anotherreactant unit present) to afford the product 16 as well as theaforementioned change in the refractive index of the holographic mediumthat produces the hologram. After sensitizing the triplet state T₁ 34 ofthe reactant species 14, the sensitizer 12 may return to the groundstate S₀ 18 to continue the process.

While one energy pathway is presented in FIG. 1, it should beappreciated that a number of other energy pathways (e.g., includingother absorption, decays, and conversions) within the system arepossible. For example, in certain embodiments, after the sensitizer 12(e.g., a M-sub-PC) has absorbed both photons to reach an excited tripletstate (e.g., T₂ 30), the sensitizer 12 may also pass the energy to anearby reactant 14 in non-radiative manner (e.g., as heat energy). Insuch embodiments, the reactant 14 may undergo a phase change (e.g.,amorphous-to-crystalline or vice versa) as a result of receiving theheat-energy from the excited sensitizer 12, which may result in a changein the refractive index of the holographic medium.

Accordingly, only regions of the optical medium that receive sufficientrecording light (e.g., beyond the intensity threshold) may experience alocalized change in refractive index. To better illustrate this effect,FIG. 2 demonstrates the threshold response of an optical mediumutilizing an RSA dye to light of varying fluence. More specifically,FIG. 2 illustrates a plot 40 of the change in the index of refraction(e.g., Δn) of a threshold material (e.g., an optical medium including anRSA dye and a reactant species) over a range of light fluences. Theillustrated plot 40 includes two curves: one curve 42 representing aread operation, and another curve 44 representing a write operation withthe holographic medium. In curve 42, the intensity of the incident lightis below the threshold (e.g., I_(th)) of the RSA material and,accordingly, regardless of the fluence of the light incident on thematerial, there is no substantial change in the refractive index of theoptical medium. In contrast, curve 44 illustrates that when the RSAmaterial is irradiated with light having an intensity above thethreshold (e.g., I_(th)) of the RSA material (as well as sufficientfluence) a substantial modulation 46 of the refractive index of thethreshold material may be observed. Accordingly, an optical mediumutilizing such an RSA dye may exhibit this non-linear response torecording light. That is, the optical medium may not demonstrate anysubstantial change in refractive index when the actinic light is below acertain intensity threshold, but demonstrate a significant change of therefractive index when the actinic light is above a certain intensitythreshold (e.g., demonstrated in curve 44). Furthermore, the hologramwritten by this change in the refractive index may be interrogated usinglight below this intensity threshold (e.g., I_(th)) such that theholographic medium may not be substantially altered during the readingprocess (e.g., demonstrated in curve 42).

To further illustrate how data may be written to the holographic medium,FIG. 3 depicts a cross-sectional view a holographic medium 50 beingexposed to recording light. More specifically, FIG. 3 illustrates aholographic medium 50 that includes an RSA dye and a reactant speciesdisposed together in a polymer matrix. Additionally, FIG. 3 illustratesthe volume 52 of the holographic medium 50 through which the recordinglight (e.g., the actinic radiation, including a reference and signalbeam) passes. Since the holographic medium 50 utilizes an RSA dye, theentire volume 52 of the holographic medium 50 does not receivesufficient recording light (e.g., above the intensity threshold of theRSA dye) to affect the modulation of the refractive index. Rather, onlythe focal point 54 (e.g., the intersection of the reference and signalbeams), receives recording light above the intensity threshold of theRSA dye and, accordingly, experiences a change in the refractive index,resulting in the writing of a hologram into the holographic medium.Accordingly, use of the RSA dye obviates undesirable chemicalmodifications in portions of the medium located near a hologram that isbeing written.

An optical medium may, in general, include an RSA dye (e.g., a M-sub-PCRSA dye) and a reactant species disposed together within a polymermatrix. In general, the polymer matrix of the holographic medium may beany polymer commonly used in the production of optical media. Forexample, the polymer may include polyalkyl (methacrylates) (PMMAs),polyvinyl alcohols, poly(alkyl acrylates), polystyrenes, polycarbonates,poly acrylates, poly(vinylidene chloride), and poly(vinyl acetate).Additionally, in certain embodiments, the reactant species may be usedto functionalize the polymer backbone (e.g., via an ester linkage topolyvinyl alcohol), as discussed in detail below. In certain embodimentsthe reactant species units may be non-covalently associated with thepolymer backbone (e.g. via. ionic interaction, hydrogen bonding, etc.).Furthermore, the RSA dye may be used in amounts of from about 0.002weight % to about 5 weight % based upon the total weight of thecomposition. In certain embodiments, the RSA dye may have aconcentration between approximately 0.01 M and 0.1 M, or a concentrationof approximately 0.4 M. Also, the support for the holographic medium maybe provided by a number of commonly employed polymer materials,including polymethyl (methacrylate) PMMA, polycarbonates, poly(ethyleneterephthalate), poly(ethylene naphthalene), polystyrene, or celluloseacetate. Additionally, the holographic medium may also includemediators, photostabilizers, plasticizers commonly known in the art.

In general, the reactant species may be any species having a tripletstate capable of undergoing a reaction (e.g., dimerization orisomerization) or a phase change (e.g., amorphous-to-crystalline or viceversa) that results in a change in the index of refraction of theholographic material. For example, in certain embodiments, the reactantspecies may be a phase-change polymer composition as disclosed in U.S.patent application Ser. No. 11/901,725, entitled, “Method for storingholographic data”, which is incorporated by reference herein in itsentirety for all purposes. In certain embodiments, the reactant may beany species capable of undergoing a refractive-index altering molecularrearrangement (e.g., [2+2] dimerization) upon being sensitized to anexcited triplet state by an excited RSA sensitizer (i.e., RSA³*). Assuch, suitable reactants include, but are not limited to, various typesof stilbenes, included halogenated stilbenes, alkylated stilbenes, cyanostilbenes, alkoxy stilbenes, or any combination thereof. Additionally,U.S. patent application Ser. No. 12,550,521, entitled, “OPTICAL DATASTORAGE MEDIA AND METHODS FOR USING THE SAME”, which is incorporated byreference herein in its entirety for all purposes, discloses examples ofcinnamate analogues that may serve as the reactant species in theholographic medium. For example, in certain embodiments, one or morecinnamate units may be bound to a polymer backbone (e.g., polyvinylalcohol) to produce a polymer structure (e.g., polyvinylcinnamate).Accordingly, when nearby cinnamate units of a polyvinylcinnamateencounter an excited RSA³* species (e.g., an excited M-sub-PC unit), anindirect photodimerization reaction may occur as indicated below:

Furthermore, in certain embodiments, the reactant species may be adiphenylcyclopropene (DPCP) derivative (e.g.,2,3-diphenylcycloprop-2-enecarboxylate) disclosed in the co-pending U.S.patent application Ser. No. 13/299,021, filed concurrently herewith,entitled “REACTANTS FOR OPTICAL DATA STORAGE MEDIA AND METHODS FOR USE”,which is incorporated by reference herein in its entirety for allpurposes. In certain embodiments, a polymer backbone (e.g., polyvinylalcohol) may be derivatized by DPCP units to form a polyvinyl-DPCPstructure. Accordingly, when nearby DPCP units of a polyvinyl-DPCPstructure encounter an excited RSA³* species (e.g., an excited M-sub-PCunit), an indirect photodimerization reaction may occur as indicatedbelow:

For cinnamate analogues, DPCP analogues, as well as other unsaturatedreactant species, a [2+2] cyclization may occur between the unsaturatedbonds of two reactant units (e.g., dimerization) once energy has beentransferred into the triplet energy level (e.g., T₁ 34) by the excitedRSA dye. Accordingly, once the RSA dye has absorbed the two photons(e.g., absorptions 20 and 28) of recording light to reach an excitedtriplet state (e.g., T₂ 30), the RSA dye may transfer the energy of theexcited triplet state 30 a reactant unit (e.g., a cinnamate-derivativeor DPCP-derivative unit) such that two reactant units may undergoindirect photodimerization. Once a substantial number ofphotodimerization events between reactant units have occurred, alocalized change in the index of refraction of the holographic mediummay be observed.

In the production of an optical medium, it is generally desirable toemploy RSA dyes having relatively high quantum efficiencies. That is, itis generally desirable to utilize RSA dyes capable of causing a greaternumber of reactant molecules to react at low recording light intensity.This high quantum efficiency enables the RSA dye to efficiently drivethe chemical reaction responsible for the modulation of the index ofrefraction of the holographic medium using lower intensity light (e.g.,fewer total photons). Accordingly, less energy may be consumed duringthe recording process, a greater number of reactant molecules may beconverted during a write operation, and/or recording times may bereduced.

In particular, U.S. patent application Ser. No. 12/551,455, entitled,“COMPOSITIONS, OPTICAL DATA STORAGE MEDIA AND METHODS FOR USING THEOPTICAL DATA STORAGE MEDIA”, which is incorporated by reference hereinin its entirety for all purposes, discloses the use of a particularnon-linear sensitizer, namely subphthalocyanine (sub-PC), as an RSA dyefor optical storage media. The sub-PC structure affords good RSAbehavior using recording light at about 405 nm (±10 nm). An example of asub-PC is shown below:

Present embodiments are directed toward the modification of the sub-PCstructure to include one or more functional groups bearing at least onemetal atom. As such, it should be noted that, while a particular sub-PCstructure is included above, this presently disclosed modification iscontemplated for any sub-PC structure. That is, any subphthalocyanineRSA that substantially responds to radiation at a wavelength less thanapproximately 500 nm (e.g., around 405 nm) may be modified according tothe presently disclosed methods for use in optical data storage media.

The present disclosure addresses modifications to the sub-PC structuregenerally relating to the addition of functionality capable of binding ametal atom to a sub-PC core structure. That is, the present embodimentsinclude metal-subphthalocyanine (M-sub-PC) derivatives, whichincorporate metal-containing functional groups or moieties into thesub-PC structure. For example, a general structure of a M-sub-PC isshown below:

where R¹ may generally be any functional group capable of binding orchelating one or more metal atoms; and each X¹ may independently beeither a proton, a halide (e.g., bromide, fluoride, chloride, iodide,etc.), a hydrocarbyl group (e.g., methyl, ethyl, t-butyl, etc.), or analkoxy (e.g., methoxy, ethoxy, etc.) group. Examples of suitablesubphthalocyanines (sub-PC) core structures include, but are not limitedto: 2,9,16-tribromosubphthalocyanato boron(III);2,9,16-triiodosubphthalocyanato boron(III); trinitrosubphthalocyanatoboron(III); 2,9,16-tri-tertbutylsubphthalocyanato boron(III);2,9,17-tri-tert-butylsubphthalocyanato boron(III); and2,9,16-triiodosubphthalocyaninato boron(III). Any of these, as well asany other subphthalocyanine core structures affording RSA behavior at awavelength of about 405 nm, may be utilized. Furthermore, it should benoted that, while in the structure included above, R¹ is illustrated asbeing bound to the boron atom, in other embodiments a metal-bearingfunctionality R¹ may be bound to any other atom of the sub-PC structure(e.g., a carbon or nitrogen atom anywhere in the structure).Furthermore, it should be noted that, in certain M-sub-PC embodiments,multiple metal-bearing groups (e.g., R¹, R², etc.) may be used toderivatize the sub-PC structure. For example, in certain embodiments,the M-sub-PC structure may (in addition or in alternative to having ametal-bearding group, R¹, bound to the boron atom) have othermetal-bearing group bound to a different atom in the structure (i.e., X¹may also include R¹ or R²).

Generally speaking, R¹ is a functional group or a collection offunctional groups that couple a metal center to the sub-PC corestructure. Accordingly, R¹ may be described by the general formula:(X²)(X³)(X⁴)(X⁵)(M)where each of X², X³, X⁴, X⁵, and M represent a portion of the structureR¹ comprising one or more atoms, as discussed in detail below. Aspresented in detail below, X² is a point of attachment for R¹ to thesub-PC core structure; X³ is a linker portion of R¹; X⁴ is the metalbinding portion of R¹; and M is the attached metal center along with anumber of associated ligands or counter-ions, X⁵. It should beappreciated that a single connection or bond may exist between thevarious portions of R¹ (e.g., X², X³, X⁴, X⁵, and M), or in certainembodiments, two or more bonds may couple these portions together (e.g.,through multiple points of attachment or multiple bonds to the samepoint of attachment). It should be further appreciated that bonds, aspresently used, refers to any chemical bond or attractive force betweentwo atoms, including covalent bonding (e.g., normal covalent bonding andcoordinate covalent bonding) and non-covalent bonding (e.g., ionicinteractions, hydrogen bonding, columbic attraction, or similarinteraction). Furthermore, while various combinations of points ofattachment (X²), linkers, (X³), metal binding portions, (X⁴), metals(M), and ligands/counter-ions (X⁵) are included in example structuresbelow, it should be appreciated that many other combinations of X², X³,X⁴, X⁵, and M are also possible and may also be used.

Generally speaking, the sensitivity of each optical medium may beassessed by considering how much the refractive index of each opticalmedium changes when irradiated using actinic light. As such, the twocurves of FIG. 7 (e.g., 62 and 64) may be compared to assess therelative sensitivity of the corresponding reactant species. For curve62, representing the cinnamate-derivative, PV-COO-cinnamate, a Δn ofapproximately 3.0×10⁻⁴ is observed when using recording light ofapproximately 800 MW/cm². In contrast, curve 64, corresponding to theDPCP-derivative, PV-COO-DPCP, illustrates a Δn of approximately 7.0×10⁻⁴when using recording light of approximately the same intensity.Accordingly, a substantial improvement in sensitivity is observed forthe holographic media utilizing DPCP-derivative reactant speciescompared to the medium utilizing the cinnamate-derivative reactantspecies. More specifically, an approximately two-fold to three-foldincrease in the Δn of holographic media utilizing the DPCP-derivativereactant species is observed when the media is exposed to recordinglight.

Additionally, in certain embodiments, R¹ may also include a linker, X³,which may couple the point of attachment (X²) to the metal bindingportion (X⁴). In general, X³ may be any atom or series of atoms (e.g.,carbon, nitrogen, oxygen, and/or protons) capable of coupling X² to X⁴.It should be appreciated that the structure of X³ may be selected toprovide particular properties. That is, in certain embodiments, X³ maybe an alkyl chain (e.g., 1 to 10 carbons in length) selected to providea non-conjugated, flexible connection to the metal binding portion (X⁴).In other embodiments, X³ may be a conjugated structure (e.g., an arenering, a polyaromatic structure, a conjugated chain, or similarstructure) selected to provide a conjugated and/or less-flexibleconnection to the metal binding portion (X⁴). In other embodiments, Rmay not include a linker X³ and, as such, the point of attachment (X²)may be directly attached to the metal-binding portion of the structure(X⁴). In still other embodiments, linkers (X³) having both saturated andunsaturated portions may be used in particular combinations to providedesired characteristics in terms of the position of the metal centerrelative to the sub-PC core structure, the electronic properties of themolecule between the metal center and the core structure, and thedesired flexibility of the linker unit.

The metal atom(s) (M) incorporated into the metal binding portion (X⁴)in the M-sub-PC structure may be any metal (e.g., indium, lead, zinc,rubidium, tin, cesium, or similar metal) or metalloid (e.g., thallium,antimony, or similar metalloid). Furthermore, in addition to the bondsto the metal bearing portion (X⁴), M may include any number of ligandsand/or counter-ions, X⁵ (e.g., to coordinatively saturate the metalcenter). For example, in some embodiments, X⁵ may comprise acetylacetone (ACAC) ligands, nitrate ligands, hydrocarbyl ligands (e.g.,methyl, ethyl, propyl, butyl), pyridine-based ligands, halidecounter-ions (e.g., chlorine, bromine, iodine, fluorine, etc.), or anyother ligands or counter-ions commonly known in the art. For example, incertain embodiments, the metal (M) may be a sodium, potassium, orrubidium atom used with an iodide counter ion (X⁵). By further example,in certain embodiments, the metal (M) may be a thallium, lead, rubidium,or cesium atom with an iodide or nitrate counter-ion (X⁵). By furtherexample, in certain embodiments (M) may be an indium, lead, or zinc atomwith two ACAC ligands or three butyl ligands (X⁵). Furthermore, incertain embodiments, metal clusters comprising a plurality of metalatoms (and possibly a number of oxygen atoms) are also contemplated foruse with the present techniques.

Furthermore, R¹ includes a metal binding portion (X⁴) which enables R¹to at least partially bind or chelate a metal atom (M). That is, X⁴ mayincorporate any functional group or moiety, or any collection offunctional groups or moieties, commonly known in the art to be used forthe attachment or chelating of metal atoms. Accordingly, generallyspeaking, X⁴ may comprise a number of atoms (e.g., carbon, nitrogen,oxygen, boron, phosphorus, or sulfur) having one or more orbitalscapable of interacting with the orbitals of the metal atom (M) such thatthe metal may be secured to the remainder of R¹. For example, asdiscussed in detail below, certain embodiments of X⁴ may include, butare not limited to, crown-ether derivatives, diketone derivatives,pyridine derivatives, porphyrin derivatives, calixarene derivatives,cyclodextrin derivatives, or similar metal-binding structures.

In certain embodiments, R¹ may be a crown-ether derivative according tothe general structure included below:

where n may be any integer from 1 to 10. By further example, R¹ mayinclude, but is not limited to, the R¹ groups depicted for the examplecrown-ether derivative structures illustrated in FIG. 4. That is, FIG. 4includes two crown-ether derivatives, namely: a 15-crown-5 derivative(RSA₁) and an 18-crown-6 derivative (RSA₂). It should be appreciatedthat while these two crown-ether derivatives are included above, anynumber of different sizes and types of hetero macrocycles may be used.For example, the crown-ether derivative portion of the M-sub-PC RSA dye(i.e., the metal binding portion X⁴ of R¹) may be a 12-crown-4 etherderivative, a 21-crown-7 ether derivative, a 24-crown-8 etherderivative, or any other crown ether derivative. Examples demonstratingthe synthesis of crown-ether derivatives are provided below.

In certain embodiments, R¹ may also be a diketone (e.g., acetyl acetone(ACAC)) derivative as indicated by the general structures includedbelow:

where each X⁶ may independently be either a proton, a hydrocarbyl grouphaving between 1 and 10 carbons, a hydroxyl group, an amino group, analkyl amino group (e.g., dimethyl amine), an alkoxy group (e.g.,methoxy, ethoxy, etc.), a halide (e.g., chlorine, bromine, iodine,fluorine, etc.), or similar species. By further example, R¹ may include,but is not limited to, the R¹ groups depicted for the example diketoneM-sub-PC structures illustrated in FIG. 5. In particular, FIG. 5illustrates diketone-based M-sub-PCs RSA₃ and RSA₄, which are similarACAC-based M-sub-PCs, with M-sub-PC RSA₄ differing from M-sub-PC RSA₃ bythree carbon alkyl linker portion (X³). FIG. 5 also illustrates M-sub-PCRSA₅ and RSA₆, which are both methoxy-ACAC derivatives where X³ is aphenylene unit. However, M-sub-PC RSA₅ illustrates the ACAC metalbinding portion (X⁴) as being coupled to the linker via the centercarbon (i.e., between the carbonyl groups), while M-sub-PC RSA₆illustrates the ACAC portion as being coupled to the linker via one ofthe carbonyl carbons. It should be appreciated that the diketones may beexist and/or be illustrated as either being the diketone or the enoltautomer.

In certain embodiments, R¹ may also be a pyridine derivative asindicated by the general structures shown below:

where each X⁷ may independently be either a proton, a carboxylic acidgroup, an alkyl ester (e.g., a methyl ester) group, an amino group, analkyl amino group (e.g., dimethyl amine), an alkoxy group (e.g.,methoxy, ethoxy, etc.), a halide (e.g., chlorine, bromine, iodine,fluorine, etc.), a hydrocarbyl group having between 1 and 10 carbons,portions of another heteroarene (e.g., pyridine ring) or other arenestructure, or similar species. By further example, R¹ may include, butis not limited to, the R¹ groups depicted for the example M-sub-PCstructures illustrated in FIG. 6. In particular, FIG. 6 depicts aphenantherene-based M-sub-PC (RSA₇), terpyridine-based M-sub-PC (RSA₈),and bis-pyridine-based M-sub-PC (RSA₉). In the illustrated embodiments,bis-pyridine-based M-sub-PC RSA₉ lacks a linker (X³) while thephenantherene-based M-sub-PC RSA₇ has a two carbon alkyl linker, and theterpyridine-based M-sub-PC RSA₈ has the longest, three carbon alkyllinker Additionally, it should be appreciated that while these threestructures (e.g., RSA₇, RSA₈, and RSA₉) illustrate specific examples ofpyridine derivative-based RSA dyes, other pyridine derivative-based RSAdyes may be utilized.

EXAMPLE 1 Synthesis of Metallated Subphthalocyanines (M-sub-PCs)

Benzo-15C5, Benzo-18C6, polyphosphoric acid, acetic anhydride, Metalsalts and subphthalocyanine-chloride (all purchased from Aldrich) wereused as received. ¹H NMR spectra were obtained on a Bruker 400 MHzspectrophotometer. UV-Vis absorption spectra were obtained on Cary UVspectrophotometer.

The synthesis routes, shown in FIGS. 7 and 8, are provided as examplesof synthesizing M-sub-PC crown-ether derivatives (e.g., RSA, and RSA₂)having an absorption minimum (i.e., RSA behavior) at 405 nm. The 15C5and 18C6 crown ether M-sub-PC derivatives were prepared. Generallyspeaking, the synthesis scheme follows a series of steps starting fromBenzo-15C5 (or Benzo-18C6 for FIG. 8) through acylation, oxidation,hydrolysis, condensation and metal incorporation, respectively, toobtain the M-sub-PC structure.

Synthesis of Metallated 15-crown-5 ether Subphthalocyanine(M/15C5-sub-PC) Derivatives

For the acylation reaction, a three neck flask was charged withpolyphosphoric acid/acetic acid (3 g/7 g), Benzo-15C5 (4.5 g, 16.77mmol), acetic anhydride (7.5 g, 3.5 equs, 58.7 mmol). The reactionmixture was stoppered, kept under nitrogen atmosphere, heated at 45° C.,and left to stir overnight. The dark brown reaction mixture was washedtwice with water (100 mL). The organic products were taken intomethylene chloride (100 mL) and dried over MgSO₄. The product waschromatographed on SiO₂ with EtOAC: Hexane=40:60 ratio eluent. Theproduct, Ac-Benzo-15C5, was isolated as pale white solid (4.5 g). ¹H NMR(CDCl₃) δ: 7.59 (d, 1H), 7.56 (s, 1H), 6.9 (d, 1H), 4.22 (m, 4H),3.9-4.0 (m, 4H), 3.8 (s, 8H), 2.59 (s, 3H).

For the oxidation step, a single neck round bottom flask was chargedwith Ac-Benzo-15C5 (4.5 g, 14.5 mmol), 20 mL CH₂Cl₂ andmetachloroperbenzoic acid (mCPBA) 1.3 equs (3.25 g, 18.87 mmol). Thereaction mixture was stoppered, kept under nitrogen atmosphere, and leftto stir overnight. The yellow precipitate reaction mixture was washedwith saturated NaHCO₃ and then twice with water (100 mL). The organicproducts were taken into methylene chloride (100 mL) and dried overMgSO₄. The product, OAc-Benzo-15C5, was isolated as yellow solid (4.51g) and used without any further purification. ¹H NMR (CDCl₃) δ: 6.9 (d,1H), 7.63 (s, 1H), 6.62 (d, 1H), 4.16 (m, 4H), 3.9 (m, 4H), 3.8 (s, 8H),2.3 (s, 3H).

For the hydrolysis step, a single neck round bottom flask was chargedwith OAc-Benzo-15C5 (3.0 g, 13.8 mmol), and hydrolyzed under refluxingconditions with aqu. NaOH (10% solution) and the reaction mixture werestirred for 3 hours under nitrogen blanket. The reaction mixture waswashed with saturated NaHCO₃ and then with water twice (50 mL). Theorganic products were taken into methylene chloride (50 mL) and driedover MgSO₄. The product, OH-Benzo-15C5, (0.6 g) was obtained was usedwithout any further purification. ¹H NMR (CDCl₃) δ: 6.75 (d, 1H), 6.44(s, 1H), 6.35 (d, 1H), 4.1 (m, 4H), 3.9 (m, 4H), 3.78 (s, 8H).

For the condensation step, a single neck round bottom flask was chargedwith subphthalocyanine chloride (0.7 g) and OH-Benzo-15C5 (0.55 g, 1.95mmol) and 10 mL toluene. The flask was fitted to a water cooledcondenser and the reaction mixture was placed in a hot oil bath andrefluxed for 3 days under a nitrogen blanket. The reaction mixture wascooled and diluted with 20 mL chloroform, washed with 10% NaOH solution,followed by a water wash. Later, the reaction mixture was suctionfiltered to remove an unreacted subphthalocyanine chloride, followed bydrying the solution with MgSO₄. The filtrate solution was removed on arotary evaporator and dried to isolate the pink product, 15C5-sub-PC,(0.25 g). ¹H NMR (CDCl₃) δ: 8.94 (m, 6H), 7.98 (m, 6H), 6.3 (d, 1H), 5.0(s, 1H), 4.9 (d, 1H), 4.2 (m, 4H), 3.9 (m, 4H), 3.6 (bs, 8H). Massanalysis: Electron Spray ToF-MS Pos Ion/90:10 acetonitrile/2 mM ammoniumformate pH=8. 15C5-sub-PC [M+H]⁺=679; MALDI (with DCTB matrix and or HBNmatrix): 15C5-sub-PC [M]⁺=678.

Metals were incorporated into the crown ether by using the followingreaction procedure. The 15C5-sub-PC (100 mg) was dissolved in 2 mL EtOHtaken in a 50 ml, round bottom flask and 1 equivalent of the metal salt(i.e., either NaI, KI, RbI or PbNO₃) was added and stirred overnight atroom temperature. The solution was later filtered through Whatmanncourse filter paper to remove any unreacted salts and the filtratesolvent was removed on a rotary evaporator. The product, M/15C5-sub-PC(i.e., Na/15C5-sub-PC, K/15C5-sub-PC, Rb/15C5-sub-PC, orPb/15C5-sub-PC), was isolated in near quantitative yield. ¹H NMR ofK/15C5-sub-PC (CDCl₃) δ: 8.94 (m, 6H), 7.98 (m, 6H), 5.9 (broad s, 1H),4.95 (broad s, 1H), 4.9 (broad d, 1H), 4.0-3.4 (broad peaks, 16H). Massanalysis: Electron Spray ToF-MS Pos Ion/90:10 acetonitile/2 mM ammoniumformate pH=8. K/15C5-sub-PC [M]⁺=717; RbI/15C5-SubPc [M]⁺=763. MALDI(with DCTB matrix and or HBN matrix): K/15C5-sub-PC [M]⁺=717;Rb/15C5-sub-PC [M]⁺=763.

Synthesis of Metallated 18-crown-6 Ether Subphthalocyanine(M/18C6-sub-PC) Derivatives

For the acylation step, a three neck flask was charged withpolyphosphoric acid/acetic acid (2 g/10.49 g), Benzo-18C6 (5 g, 16mmol), acetic anhydride (8.16 g, 5 equs, 80 mmol). The reaction mixturewas stoppered, kept under nitrogen atmosphere, heated at 45° C., andleft to stir overnight. The dark brown reaction mixture was washed twicewith water (100 mL). The organic products were taken into methylenechloride (100 mL) and dried over MgSO₄. The product was chromatographedon SiO₂ with EtOAC: Hexane=40:60 ratio eluent. The product,Ac-Benzo-18C6, was isolated as pale white solid (5.2 g). ¹H NMR (CDCl₃)δ: 7.59 (d, 1H), 7.56 (s, 1H), 6.9 (d, 1H), 4.22 (m, 4H), 3.9-4.0 (m,4H), 3.6-3.8 (m, 12H), 2.6 (s, 3H).

For the oxidation step, a single neck round bottom flask was chargedwith Ac-Benzo-18C6 (4.7 g, 13.27 mmol), 20 mL CH₂Cl₂ andmetachloroperbenzoic acid (mCPBA) 1.5 equs (2.5 g, 19.9 mmol). Thereaction mixture was stoppered, kept under nitrogen atmosphere, and leftto stir overnight. The yellow precipitate reaction mixture was washedwith saturated NaHCO₃ and then twice with water (100 mL). The organicproducts were taken into methylene chloride (100 mL) and dried overMgSO₄. The product, OAc-Benzo-18C6, was isolated as yellow solid (4.71g) and used without any further purification. ¹H NMR (CDCl₃) δ: 6.9 (d,1H), 6.63 (s, 1H), 6.62 (d, 1H), 4.20 (m, 4H), 3.9 (m, 4H), 3.8-3.6 (m,12H), 2.3 (s, 3H).

For the hydrolysis step, a single neck round bottom flask was chargedwith OAc-Benzo-18C6 (1.2 g, 3.24 mmol), and hydrolyzed under refluxingconditions with aq. NaOH (10% solution) and the reaction was stirred for3 hrs under a nitrogen blanket. The reaction mixture was washed withsaturated NaHCO₃ and then twice with water (50 mL). The organic productswere taken into methylene chloride (50 mL), dried over MgSO₄. Theproduct, OH-Benzo-18C6, (0.6 g) was obtained was used without anyfurther purification.

For condensation reaction, subphthalocyanine chloride and OH-Benzo-18C6(3.0 g) were added to a single neck round bottom flask in stoichiometricequivalents and dissolved in 10 mL toluene. The flask was fitted to awater cooled condenser and the reaction mixture was placed in a hot oilbath and refluxed conditions for 3 days under a nitrogen blanket. Thereaction mixture was cooled, diluted with 20 mL chloroform, washed with10% NaOH, followed by washing with water. Later, the reaction mixturewas suction filtered to remove any unreacted subphthalocyanine chloride,followed by drying the solution using MgSO₄ to yield a pink compound,18C6-sub-PC. The filtrate solution was removed on a rotary evaporaterand dried. ¹H NMR of 18C6-sub-PC (CDCl₃) δ: 8.9 (m, 6H), 7.98 (m, 6H),6.69 (d, 1H), 6.67 (s, 1H), 6.4 (d, 1H), 4.0-3.6 (m, 20H).

Metals were incorporated into the crown ether using the followingreaction procedure. The 18C6-sub-PC (30 mg, 3×10⁻³ mmol) was dissolvedin 2 mL EtOH taken in a 50 mL round bottom flask and 1 equivalent of themetal salt (i.e., NaI, KI, RbI or PbNO₃) was added and the reaction wasstirred overnight at room temperature. The solution was later filteredthrough Whatmann course filter paper to remove any unreacted salts andthe filtrate solvent was removed on a rotary evaporator to give a pinkproduct, M/18C6-sub-PC. ¹H NMR of Pb/18C6-sub-PC (CDCl₃) δ: 8.9 (m, 6H),7.98 (m, 6H), 6.79 (d, 1H), 6.78 (s, 1H), 6.5 (d, 1H), 4.2-3.8 (m, 20H).Mass analysis: Electron Spray ToF-MS Pos Ion/90:10 acetonitile/2 mMammonium formate pH=8. MALDI (with DCTB matrix and HBN matrix):PbNO₃/18C6-sub-PC [M]⁺=1020.

Additionally, Table 1 indicates certain absorption characteristics of anumber of RSA dyes based on UV/Vis absorption analysis in chloroform.More specifically, the λ_(max), ε_(max), and ε₄₀₅ values for a number of15C5-sub-PC RSA dyes and a Pb/18C6-sub-PC RSA dye are included.

TABLE 1 Crown SubPcs λ_(max)/nm^(a) ε_(max)/M⁻¹cm⁻¹ ε_(405 nm)/M⁻¹cm⁻¹15C5-sub-PC 562 52390 436 K/15C5-sub-PC 562 48986 449 Rb/15C5-sub-PC 56459943 407 Pb/18C6-sub-PC 566 48009 331

Microhologram Recording

As discussed in detail below, the inclusion R¹, with its metal bearingfunctionality (X⁴) affords improved sensitivity over the sub-PCstructure alone. That is, the presently disclosed M-sub-PC embodimentsafford higher quantum efficiencies using recording light of lowerintensity than the previously disclosed sub-PC structure. While notwishing to be limited to any particular mechanism, generally speaking,the presence of metal atoms is believed to enhance the rate ofintersystem crossing (ISC) (e.g., ISC 24), which in turn, may afford theobserved enhanced quantum efficiency of the system. One way of measuringthe sensitivity of an RSA dye is to determine the change in therefractive index of an optical medium utilizing the RSA dye as afunction of the intensity of actinic light used to record data to theoptical medium. Refractive index measurements may be performed using anellipsometer to measure bulk materials (e.g., using spin coatedsamples). Thus, the reactive materials used in these applications may betested to determine the net change in the refractive index, Δn, of thematerial by measuring the refractive index, n, of the sample before andafter exposure to actinic radiation of varying intensity (constantfluence).

For example, FIG. 9 is a graph 80 illustrating the change in therefractive index of different optical media being exposed to actinicradiation (e.g., around 405 nm) of varying intensity (constant fluence).More specifically, FIG. 9 illustrates curves for three different opticalmedia, as described above, each utilizing a different RSA dye having theM-sub-PC general structure. As illustrated, the curve 84 corresponds tothe general M-sub-PC structure, where R is a phenoxy group. That is,curve 84 reflects the Δn of an irradiated optical medium that includes anon-metallated-sub-PC as the RSA dye. In contrast, curves 86 and 88reflect the Δn of irradiated optical media that utilizemetallated-sub-PC sensitizers. In particular, curve 86 depicts the Δn ofan irradiated optical medium that uses a M-sub-PC RSA dye, where R¹comprises X², X³, X⁴, X⁵, and M; and where X² is an oxygen atom; X³ isan arene linker; X⁴ is a 15-crown-5 ether-based metal binding portion; Mis a rubidium atom; X⁵ is an iodide counter-ion (i.e., Rb/15C5-sub-PC).Furthermore, curve 88 depicts the Δn of an irradiated optical mediumthat uses a M-sub-PC RSA dye, where R¹ comprises X², X³, X⁴, X⁵, and M;and where X² is an oxygen atom; X³ is an arene linker; X⁴ is a18-crown-6 ether-based metal binding portion; M is a lead atom; X⁵ is anitrate counter-ion (i.e., Pb/18C6-sub-PC).

Generally speaking, the sensitivity of each optical medium may beassessed by considering how much the refractive index of each opticalmedium changes when irradiated using actinic light of relatively lowintensity. As such, the three curves of FIG. 9 (e.g., 84, 86, and 88)may be compared to assess the relative sensitivity of the threecorresponding RSA dye structures. For curve 84, representing the sub-PCstructure alone (i.e., not metal substituted), a Δn of approximately4.0×10⁻⁶ is observed when using recording light of approximately 425MW/cm². In contrast, curve 86, corresponding to the Rb/15C5-sub-PC RSAdye, illustrates a Δn of approximately 2.2×10⁻⁵ when using recordinglight of approximately the same intensity. Furthermore, curve 88,corresponding to the Pb/18C6-sub-PC RSA dye, illustrates a Δn ofapproximately 3.7×10⁻⁵ when using recording light of approximately thesame intensity. Accordingly, a substantial improvement in sensitivity isobserved for the holographic media utilizing M-sub-PC RSA dyes comparedto the medium utilizing the non-metal substituted sub-PC RSA dyestructure. That is, an approximately five-fold to nine-fold increase inthe Δn of holographic media utilizing M-sub-PC RSA dyes is observed whenthe media is exposed to recording light of low intensity.

Furthermore, the quantum efficiency for each of the optical mediaillustrated in FIG. 9 may also be determined. More specifically, thesequantum efficiencies (which are discussed in detail below with respectto FIG. 10) may be determined using a quantum efficiency measurementsetup, such as the one illustrated in FIG. 11. That is, FIG. 11illustrates a schematic of an embodiment of a quantum efficiencymeasurement setup 100 for performing the quantum efficiency measurement.In the illustrated setup 100, a pump beam 102 (e.g., from a laser source103 capable of producing light having a wavelength of approximately 405nm) and UV probe beam 104 (e.g., from a UV lamp 105 capable of producingwavelengths of approximately 280 nm to 360 nm) are incident on a sample106 in a counter-propagating geometry. The beams 102 and 104 may befocused on a surface of the sample 106 by a number of respectiveobjectives and/or lenses 108 (e.g., microscope UV objectives and UVquartz lenses with UV anti-reflecting coatings). Additionally, the spot110 of the focused pump beam 102 (which may be approximately 20 um indiameter at the surface of the sample 106) and the spot 112 of thefocused UV probe beam 104 may be configured to overlap at the surface ofthe sample 106. Furthermore, after the UV probe beam 104 has traversedthe sample 106, UV probe beam 104 passes a dichromic mirror 114 and issubsequently focused by a number of objectives and/or lenses 108 (e.g.,a UV objective) onto the approximately 20 um pinhole entrance 116 to aUV/Vis spectrometer 118. The collecting optics may be configured to havemagnification close to 1 and, therefore, the spot 110 may be imagedusing a detector pinhole of the approximately the same size (e.g.,approximately 20 um), resulting in a confocal detection configuration.As such, the diameter of the spot 112 of the focused UV probe beam 104may be larger than the spot 110 of the focused pump beam 102; however,the confocal geometry of the illustrated setup 100 may limit the probingregion to approximately 20 um.

The illustrated setup 100 enables measuring the change in the absorbanceof the index change material (e.g., the sample 106) as a function of thefluence of the pump beam 102 using the UV probe beam 104. F₀, which maybe considered the fluence number where the absorbance is zero, may beapproximated using an absorbance versus fluence plot 140, illustrated inFIG. 12, using data obtained via the setup 100. In the illustrated plot140, the slope of the illustrated line 142 approximately equals 1/F₀.Using this derived F₀, the quantum efficiency, Q(I), of the energytransfer process may be calculated using the following equation:

$\begin{matrix}{{{Q(I)} = \frac{hv}{{F_{0}(I)}{\sigma_{RSA}(I)}}},} & {{Eq}.\mspace{14mu} 1}\end{matrix}$wherein σ_(RSA)(I) is the RSA excited absorption cross section. Forexample, the quantum efficiency could be measured at differentintensities to verify the threshold behavior of the sample 106.

The quantum efficiency for each of the optical media illustrated in FIG.9 may also be determined using the setup 100 described above, withrespect to FIG. 11. Accordingly, FIG. 10 is a graph 90 illustratingthree curves (e.g., 92, 94, 96) corresponding to the quantumefficiencies of the three optical media described above, with respect toFIG. 9. As such, for curve 92, corresponding to the non-metalsubstituted sub-PC structure, a quantum efficiency of approximately0.0025 at an intensity of approximately 425 MW/cm² is observed. Incontrast, for curve 94, corresponding to the Rb/15C5-sub-PC RSA dye, aquantum efficiency of approximately 0.007 is observed at approximatelythe same intensity. Furthermore, for curve 96, corresponding to thePb/18C6-M-sub-PC RSA dye, a quantum efficiency of approximately 0.011 isobserved at approximately the same intensity. Accordingly, theimprovement in the quantum efficiency when recording with an opticalmedium having a M-sub-PC RSA dye and low recording light intensity mayrange from approximately three-fold to more than four-fold.

Technical effects of the invention include the manufacture ofholographic media having greater sensitivity and quantum efficiency thanpreviously achieved. As described above, the disclosed M-sub-PC RSA dyesprovide relatively high quantum efficiencies when using relativelylow-intensity recording light. These improved sensitivities enable thewriting of microholograms in the nanosecond time scale usinglow-intensity light around 405 nm, allowing many more layers of data tobe written compared to other wavelengths (e.g., 532 nm). This enablesthe development of hologram-based, high-density data storage systems anddevices.

While only certain features of the invention have been illustrated anddescribed herein, many modifications and changes will occur to thoseskilled in the art. It is, therefore, to be understood that the appendedclaims are intended to cover all such modifications and changes as fallwithin the true spirit of the invention.

The invention claimed is:
 1. An optical storage medium compositioncomprising: a polymer matrix; a reactant disposed within the polymermatrix and capable of undergoing a modification that alters therefractive index of the composition upon receiving an energy transferfrom an excited sensitizer; a non-linear sensitizer disposed within thepolymer matrix and comprising a subphthalocyanine (M-sub-PC) reversesaturable absorber configured to become excited upon exposure to lighthaving an intensity above an intensity threshold and configured totransfer energy to the reactant, wherein the M-sub-PC comprises: asubphthalocyanine portion, a linker portion, a metal binding portion,and a metal portion, and wherein the metal portion comprises one or moreof: indium, lead, zinc, tin, cesium, thallium, antimony, sodium,potassium, or rubidium.
 2. The optical storage medium of claim 1,wherein the modification comprises a chemical reaction or a physicalstate-change of a portion of the composition.
 3. The optical storagemedium of claim 1, wherein the energy transfer comprises a radiativeenergy transfer, a non-radiative energy transfer, or any combinationthereof.
 4. The optical storage medium of claim 1, wherein the reactantcomprises one or more of a stilbene derivative, a cinnamate derivative,a diphenylcyclopropene (DPCP) derivative, or a phase-change polymer. 5.The optical storage medium of claim 4, wherein the polymer matrixcomprises a polymer chain and the reactant comprises one or more of astilbene derivative, a cinnamate derivative, or a diphenylcyclopropene(DPCP) derivative coupled to the polymer chain.
 6. The optical storagemedium of claim 1, wherein the subphthalocyanine portion of the M-sub-PCcomprises subphthalocyanato boron(III); 2,9,16-tribromosubphthalocyanatoboron(III); 2,9,16-triiodosubphthalocyanato boron(III);trinitrosubphthalocyanato boron(III);2,9,16-tri-tertbutylsubphthalocyanato boron(III);2,9,17-tri-tert-butylsubphthalocyanato boron(III); or2,9,16-triiodosubphthalocyaninato boron(III).
 7. The optical storagemedium of claim 1, wherein the metal binding portion comprises one ormore of: a crown-ether derivative, diketone derivative, pyridinederivative, porphyrin derivative, calixarene derivative, or cyclodextrinderivative.
 8. The optical storage medium of claim 1, wherein theM-sub-PC comprises a ligand portion comprising one or more of diketoneligands, nitrate ligands, alkyl ligands, pyridine-based ligands, orhalide counter-ions.
 9. The optical storage medium of claim 1, whereinthe optical storage medium is capable of storing data as one or moremicroholograms on the optical storage medium, wherein the one or moremicroholograms are configured to store information about the intensityand phase of the light.
 10. The optical storage medium of claim 1,wherein the optical storage medium comprises a non-linear sensitizerconcentration between approximately 0.01 M and 0.1 M.
 11. The opticalstorage medium of claim 1, wherein the optical storage medium comprisesa non-linear sensitizer concentration of approximately 0.04 M.
 12. Theoptical storage medium of claim 1, wherein the polymer matrix comprisesone or more poly(alkyl methacrylates), poly(alkyl acrylates),polystyrenes, polycarbonates, poly acrylates, poly(vinylidenechlorides), or poly(vinyl acetates).
 13. The optical storage medium ofclaim 1, wherein the M-sub-PC reverse saturable absorber is configuredto respond to light having a wavelength of approximately 405 nm.
 14. Theoptical storage medium of claim 1, wherein the linker portion is axiallybound to a central boron atom of the subphthalocyanine portion of theM-sub-PC.
 15. A triplet sensitizer having the formula:

wherein: each X¹ independently comprises: a proton, a halide, ahydrocarbyl group having between 1 and 10 carbons, or an alkoxy grouphaving between 1 and 10 carbons; and R¹ consists of: a linker portioncomprising at least one oxygen atom; a metal binding portion; and ametal portion; wherein the sensitizer is a reverse saturable absorber(RSA) dye, and wherein R¹ comprises a crown-ether moiety or a diketonemoiety.
 16. The sensitizer of claim 15, wherein R¹ has the generalformula:

wherein: n is between 1 and 10; and M comprises indium, lead, zinc, tin,cesium, thallium, antimony, sodium, potassium, or rubidium; and X⁵comprises one or more ligands or counter ions.
 17. The sensitizer ofclaim 16, wherein R¹ has the formula:


18. The sensitizer of claim 15, wherein R¹ has the general formula:

wherein: each X⁶ independently comprises: a proton, a hydrocarbyl grouphaving between 1 and 10 carbons, a hydroxyl group, an amino group, analkyl amino group having between 1 and 4 carbons, an alkoxy group havingbetween 1 and 10 carbons, a phenoxy group, or a halide; X³ comprisesalkyl chain or an arene structure having between 1 and 10 carbons; Mcomprises indium, lead, zinc, tin, cesium, thallium, antimony, sodium,potassium, or rubidium; and X⁵ comprises one or more ligands or counterions.
 19. The sensitizer of claim 18, wherein R¹ has the formula:


20. The sensitizer of claim 15, wherein the metal portion comprises oneor more of indium, lead, tin, cesium, thallium, antimony, sodium,potassium, or rubidium.
 21. A method for storing data on an opticalmedium comprising: irradiating a portion of the optical medium withrecording light having an intensity above an intensity threshold,wherein the optical medium comprises a subphthalocyanine (M-sub-PC)reverse saturable absorber (RSA) and a reactant disposed within apolymer matrix, wherein the M-sub-PC comprises: a subphthalocyanineportion, a linker portion coupled to both the subphthalocyanine portionand a metal binding portion, and a metal portion coupled to the metalbinding portion; exciting the M-sub-PC RSA to an excited triplet statewith the recording light such that the excited M-sub-PC RSA sensitizes amodification of the reactant; and modifying the reactant such that therefractive index of the portion of the optical medium is altered,forming a hologram on optical medium, wherein the hologram storesinformation about the intensity and phase of the recording light. 22.The method of claim 21, comprising interrogating the portion of theoptical medium using lower intensity light than the recording light suchthat the information stored in the hologram can be non-destructivelyrecovered.
 23. An optical storage medium composition comprising: apolymer matrix; a reactant disposed within the polymer matrix andcapable of undergoing a modification that alters the refractive index ofthe composition upon receiving an energy transfer from an excitedsensitizer; a non-linear sensitizer disposed within the polymer matrixand comprising a subphthalocyanine (M-sub-PC) reverse saturable absorberconfigured to become excited upon exposure to light having an intensityabove an intensity threshold and configured to transfer energy to thereactant, wherein the M-sub-PC comprises: a subphthalocyanine portion, alinker portion, a metal binding portion, and a metal portion, whereinthe linker portion comprises an alkoxy or aryloxy moiety.